Electrode structure



Dec. 12, 1939. w, HENNEBERG ET AL 2,182,869

ELECTRODE STRUCTURE Filed Feb. 19, 1937 INVENTORS WALTER HENNEBERG ALFRED RECKNAGEL 5 ATTORNEY plates.

Patented Dec. 12, 1939 UNITED STATES PATENT oFFrcs ELECTRODE STRUCTURE many Application February 19, 1937, Serial No. 126,546

In Germany February 29, 1936 7 Claims.

This invention relates to electrode structures, and in particular, to electrostatic deflecting systems for cathode ray tubes.

In order to deflect electron rays such as are obtained in cathode ray tubes for instance, pairs of deflection plates or pairs of deflection coils are used. Now, it is known that aside from their capability to deflect, these deflection elements are also capable of exerting a focusing effect upon the electron ray. Thus such a deflection element represents an additional cylinder lens which varies in an undesirable manner the optical prop! erties of the electron-optical system likewise contained in the tube.

In order to avoid the focusing efiects of the deflection element, it has already been suggested to resort to a superposition of electrical and magnetic fields.

In accordance with the invention a deflection element dev id of focusing action can already be obtained by the use of a single and suitably chosen electrical field. To this end the field is placed axially symmetrical such that the radially directed electrical field intensity decreases in the inverse sense in which the third power of the distance from the axis decreases.

The invention will now be explained in its particulars with reference to the drawing showing by way of example a mode of construction of electrodes wh ch produce the field prescribed in accordance with the invention. In the drawing items and 2 designate plates having a preferably circular shape and formed of resistance material the nature of which will be described below, said plates having arranged thereon concentrically the one pair of electrodes 3 and 4, and rings and 6 are placed around said plates forming the other pair of electrodes of the deflection element. The electrodes 5 and 5 are suitably designed as concentric w res and rings. The resistance material is such that with an increase in distance from the axis 1 of the system, the electric potential decreases in accordance with 1/r b. The field intensity and the potential assume almost the same course in the free space between the resistance A resistance material of the type desired can as is known be produced in various ways. For instance there may either be used a homogeneous material with varying thickness, or a suitable non-homogeneous material. In order to provide a deflection of an electron ray, the potential at the central electrodes 3 and 4 is chosen positive and that at the outer electrodes 5 and 6 negative. With suitable choice of the electron velocity and deflection potential it can be accomplished that a beam of electrons enclosed within a plane between the resistance plates and extending at right angles to the axis describes an almost circular course in this plane. This pencil of rays will not be focused.

In place of resistance material continuously passed by a weak current, a dielectric may likewise be used in which a central electrode is embedded, and around which a second ring-shaped electrode is arranged. The dielectric must have such inhomogeneity that the field intensity assumes the required course namely inversely proportional to the third power of the distance.

What we claim is:

1. A cathode ray tube deflecting system comprising two parallelly spaced coaxial imperforate planar conducting disks, an annular cylindrical conducting member surrounding and in contact with each of the said disks, a conductor connected to each of said members, and a conductor connected to the center of each of said disks whereby potentials may be supplied between the center and periphery of each of said disks.

2. A cathode ray deflecting system comprising a first conducting imperforate planar disk, the conductivity of said disk varying inversely as a function of the distance from the center to the periphery of said disk, a second disk substantially similar to said first disk, said second disk being parallel to and coaxial with the first named disk, a

cylindrical conducting member surrounding and in contact with each of the said disks and conductors for supplying potentials both to the conducting members and to the center of each of said disks.

3. A cathode ray deflecting system comprising a first imperforate conducting disk whose conductivity varies inversely as the third power of the distance measured from the center of the disk toward the periphery, a second imperforate conducting disk similar to said first disk, said second disk being positioned parallel to and coaxial with the first disk, and a cylindrical conducting member concentric and in contact with each of the disks.

4. A cathode ray deflecting system comprising two parallelly spaced imperforatc conducting disks, a cylindrical conducting member concentric and in contact with each of the disks, means to connect the center of each of the disks together, and means to connect the cylindrical members together whereby potentials may be supplied between the center and periphery of the disks.

5. A cathode ray deflecting system comprising two parallelly spaced imperforate non-uniform conducting disks, a cylindrical conducting member concentric and in contact with each of the disks, means to connect the center of each of the disks together, and means to connect the cylindrical members together whereby potentials may be supp-lied between the center and periphery of the disks.

6. A cathode ray deflecting system comprising two parallelly spaced imperforate non-uniform conducting disks, the conductivity of said disks varying inversely as the third power of the distance measured from the center toward the periphery, a cylindrical conducting member concentric and in contact with each of the disks, means to connect the center of each of the disks together, and means to connect the cylindrical members together whereby potentials may be supplied between the center and periphery of the disks.

'7. In a cathode ray tube wherein is produced a focused beam of electrons, the method of defleeting the beam of electrons by an electrostatic field without disturbing the focus, thereof, which comprises the step of superimposing upon the deflecting electrostatic field an axially symmetrical electrostatic field whose intensity varies inversely as the third power of the distance measured from the axis of symmetry, the lines of force of said superimposed electrostatic field being parallel to the lines of force of the deflecting electrostatic field.

WALTER HENNEBERG. ALFRED RECKNAGEL. 

